turnip: Two ubsan fixes
Fixes two issues:
src/freedreno/vulkan/tu_pipeline.c:1722:72: runtime error: index 5 out of bounds for type 'uint64_t [5]'
src/freedreno/vulkan/tu_autotune.c:509:48: runtime error: division by zero
There are also a few zero-sized VLAs happening, but they are less important.